The launcher should now be stabilized and usable on all three supported platforms including Mac!
With a lot of effort on our part, the Mac & Linux client should work just like the Windows client.
edit: If you are having an issue on Mac with the game opening for a second then closing, install the latest JDK: http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html